Avaliação das propriedades antitumorais de complexos de rutênio(II) contendo os ligantes lapachol ou lausona

Abstract

Metal complexes containing ligands that present biological activity have been attracting interest in the field of development of new drugs for the treatment of cancer. Lapachol and lawsone are examples of important natural products that exhibit antitumor properties. Thus, in the present work, new ruthenium(II) complexes containing lapachol or lawsone, phosphinic and bipyridine ligands, were synthesized and characterized, in order to obtain potential antitumor agents. Complexes were obtained with the following structural formulas: [Ru(L)(P-P)(bipy)]PF6 and [Ru(L)(P-P)2]PF6, where L = lapachol or lawsone, P-P = dppf = 1,1’-bis(diphenylphosphine)ferrocene, dppe = 1,2’-bis(diphenylphine)ethane, dppm = bis(diphenylphosphine)methane and bipy = 2,2’-bipyridine. The complexes were characterized by the techniques: elemental analysis, conductimetry, absorption spectroscopy in the infrared and in the visible ultraviolet region, cyclic and differential pulse voltammetry, 31P{1H}, 1H and 13C nuclear magnetic resonance, and X-ray diffraction of monocrystal (for the cases in which it was possible to obtain crystals). DNA interaction studies using spectroscopic titration, circular dichroism, agarose gel electrophoresis and fluorescence techniques showed that the complexes interact with the DNA by minor grooves. Analysis of the ability to interact with BSA by fluorescence measurements, allowed to conclude that the complexes exhibit a moderate interaction with the protein, with binding constants in the order of 104 - 105 M. In addition, the interactions occurred spontaneously, as evidenced by the negative values of ΔG°, involving hydrophobic and electrostatic forces. The cytotoxic activity of the complexes was investigated using the tumor cell lines of breast (MDA-MB-231 and MCF-7), lung (A549), prostate (DU-145) and non-tumor breast (MCF-10A) and fibroblast of gingiva (FGH). All complexes were active against the evaluated cell lines, presenting IC50 values lower than those obtained for the precursor complexes, free ligands and cisplatin. The complexes [Ru(lap)(dppe)(bipy)]PF6 and [Ru(lap)(dppm)2]PF6 showed to be more selective against breast tumor cells, MDA-MB-231, when compared to results obtained for non-tumor cells, MCF-10A. Therefore, these complexes were selected for the investigation of the possible mechanism of action against the MDA-MB-231 cells. Studies showed that these complexes caused greater changes in the morphology of MDA-MB-231 than in MCF-10A cells. In addition, the complexes showed to be able to act in the colonies formation process, reducing the number and size of the colonies. Cell migration assays have shown that the complexes act inhibiting the cell migration process. Another interesting property observed for the complexes was that they inhibit the formation of tubes in HUVEC cells, with or without FGF-2 growth factor, demonstrating that the complexes are antiangiogenic. Cell cycle analysis of MDA-MB-231 cells showed accumulation of cells in Sub-G1 phase, with a decrease in S phase. Cell accumulation assays showed that the complexes exhibit a greater accumulation in MDA-MB-231 than in non-tumor cells, MCF-10A. The complexes induced cell death by apoptosis, caused depolarization of the membrane potential of mitochondria, and induced ROS formation. In addition, was observed the activation of protective cell signaling through Hsp27, Bad, caspase 3, SAPK/JNK and Smad pathways. Given these results, the oxidative stress is a possible mechanism of cell death for the proposed complexes. The obtained results indicate that ruthenium complexes containing lapachol or lawsone present promising properties for the development of new chemotherapeutics for the treatment of cancer.